No Audio from Shruthi and intermittent MIDI response [solved]

Hi I’ve managed to assemble my Shruthi but I can’t get any audio out of it apart from pops and it responds to MIDI only intermittently every few notes or so. I did have a problem where the 7805 ground pin came unconnected but I have managed to fix that and I am getting the proper 5 volts at the +5V pin. Any suggestions as to what may have gone wrong or what I can do…?

Presumably as well as at point 7 I should be able to hear the tone at the other end of the resistor or on the pin of the LM13700 where the signals are mixed?

Here are some more relevant photos

Intermittent MIDI: check that there is no bent pin on the optocoupler (and check the solder joints of this part too - or at least what you can access without removing the LCD).

No audio: trace the signal through the filter board as explained at the end of the filter board assembly instructions.

Scratch the MIDI problem that is working normally my interface was at fault there but I still only get pops. Changing patches changes the loudness of these pops in some instances if that is of any help.

Only to an extent… out of ten million possible causes this may have ruled out a dozen or so… Your best option is to do as Olivier suggested; trace the audiopath. It’s not only the most direct way of solving this kind of issues but it’ll also teach you a lot about what each part of the circuit does to the sound.

Hi pichenettes thanks for the response the MIDI problem isn;t to do with the Shruthi. I’ve tested the filter board and get audio up until point 5 but I can’t see anything obviously wrong any more suggestions?

Thanks for the response ByteFrenzy I know there are still a myriad of possible problems I was just trying to narrow it down as best I can. I’ve just taken a couple of photos of the board that I’ll upload in a second to see if you more experienced guys can spot anything

Post a photo of your board. Probably wrong resistor values somewhere, or a bad solder joint on the TL074 or LM13700s.

Here you go

Ok I found an out of place pin on the left most LM13700 that has fixed the problem up until point 8 where I just get the popping sound.

I have now fixed the problem I cracked out my soldering iron and resoldered any of the joints that looked even slightly suspect in the area and it’s now working. Sorry for wasting your time and thanks very much for the help.